# Line-trap tuning-unit reference Canonical URL: https://eloragrid.ai/symbols/line-trap-tuning-unit-reference Publisher: Elora Grid Updated: 2026-11-03 Lookup label: LTR Drawing use: Schematic Reference families: Manufacturer Representation: Functional block Installation focus: switchyards Input: Carrier-frequency circuit Output: Assigned trap tuning function Identifies the documented tuning assembly associated with the selected line trap. ## In plain English ### What this block does Identifies the documented tuning assembly associated with the selected line trap. ### A simple example In a switchyard line bay, carrier-coupling equipment can connect a protection communication terminal to the transmission conductor. Fiber-based protection uses another physical path but still needs named endpoints and channel supervision. For this reference, the drawing identifies “Carrier-frequency circuit” at the input and “Assigned trap tuning function” at the output. Tuning characteristics require the selected equipment data. ### What the drawings help you do Start at the named input: Carrier-frequency circuit. Identify its source device or document and the state represented on the drawing. Follow the named output: Assigned trap tuning function. Cross-reference its destination and separate the command from confirmation that the equipment responded. ### Terms - Input: Carrier-frequency circuit - Output: Assigned trap tuning function - Application reference: An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections. Concept diagram: Carrier-frequency circuit → LTR → Assigned trap tuning function A reading guide. The entry's original illustration and input/output facts describe this application. - [Line traps: power-line carrier communication](https://www.gevernova.com/grid-solutions/sites/default/files/2025-09/Line-Traps-Brochure-EN-N50059-Hybrid-202504-R002.pdf) ## What it represents Identifies the documented tuning assembly associated with the selected line trap. A protection communication interface carries information between circuit ends or couples a communication signal to a primary line. Its signal path is different from the power-current path even when both use part of the same installation. In a switchyard line bay, carrier-coupling equipment can connect a protection communication terminal to the transmission conductor. Fiber-based protection uses another physical path but still needs named endpoints and channel supervision. For this reference, the drawing identifies “Carrier-frequency circuit” at the input and “Assigned trap tuning function” at the output. Tuning characteristics require the selected equipment data. Show each coupling boundary and the intended information direction. Frequency selection, channel performance, insulation duty and protective coordination require the selected communication and primary equipment design. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation. ## How to read it - Start at the named input: Carrier-frequency circuit. Identify its source device or document and the state represented on the drawing. - Follow the named output: Assigned trap tuning function. Cross-reference its destination and separate the command from confirmation that the equipment responded. - Tuning characteristics require the selected equipment data. - Show each coupling boundary and the intended information direction. Frequency selection, channel performance, insulation duty and protective coordination require the selected communication and primary equipment design. ## Information to show or reference - Label the source and connection reference for carrier-frequency circuit. - Identify the destination and defined state of assigned trap tuning function. - Record the equipment or control-document revision supporting this functional block. - Check this application limit in the project design: Tuning characteristics require the selected equipment data. ## Important distinction Tuning characteristics require the selected equipment data. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram. ## Facts - Representation: Functional block - Installation focus: Switchyards - Input / boundary: Carrier-frequency circuit - Output / connection: Assigned trap tuning function - Lookup label: LTR is a library lookup label, not a standard device designation. ## Public references - [Line traps: power-line carrier communication](https://www.gevernova.com/grid-solutions/sites/default/files/2025-09/Line-Traps-Brochure-EN-N50059-Hybrid-202504-R002.pdf) — GE Vernova. Public technical context for line carrier and protection communication interfaces. Line traps, coupling and power-line carrier communications. The application text and educational graphic are independently authored; the publisher does not certify this representation. ## Graphic scope Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.